SRS error when accessing Oracle spatial based WFS layer from GWP

We have two point features that were created as Oracle Spatial features using dgn2sdo and have been defined in GWP as separate WFS features.  When I query the items through the example site data is returned, all good.  When I try to read the features through an OCG compliant viewer, I can see the features, but when I select them I get the following error in the GWP log:

An error occurred : The GML Writer requires a Spatial Reference System set on the features to write proper GML.

Any ideas?